Russian Soyuz-FG rocket with the Soyuz TMA-12M spacecraft and a crew of US astronaut Steven Swanson, Russian cosmonauts Alexander Skvortsov and Oleg Artemyev aboard, blasts off from a launch pad at the Russian-leased Baikonur cosmodrome in Kazakhstan, early on March 26, 2014. Image: AFP / Getty Images.

A month ago, as tensions escalated between Russia and Ukraine, we wondered about the fallout for the American space program—what would happen if the diplomatic crisis got so bad that Russia refused to fly American astronauts?

Well, things aren't that bad yet, but the Cold War revival is putting a chill on space-based cooperation. NASA associate administrator Michael F. O'Brien issued a statement this morning saying: "Given Russia's ongoing violation of Ukraine's sovereignty and territorial integrity, until further notice, the U.S. Government has determined that all NASA contacts with Russian Government representatives are suspended, unless the activity has been specifically excepted."

"Specifically excepted" is the key phrase here. So far, the only thing to qualify is the slate of missions to the International Space Station, since the U.S. currently cannot send or retrieve its people from orbit without Russian spacecraft.